This application is based on an application No. 11-354835 filed in Japan, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a throw-away tip for use in a cutting process.
2. Description of Related Art
Throw-away tips are known which are adapted to be attached to a holder or the like to function as a cutting tool. Such a throw-away tip is a disposable tip which is changed, rather than polished for reuse, when its cutting edge is worn out. The throw-away tip has cutting ridges provided on respective corners of a generally planar rectangular or triangular base. When one of the corner cutting ridges is worn out, another of the corner cutting ridges is used. Then, the throw-away tip is changed when all the corner cutting ridges are worn out.
However, it is not easy to check how far the cutting ridges of the throw-away tip have been worn. In view of an operating environment, it is particularly difficult to detect the abrasion degree of a cutting ridge currently used for cutting without interrupting the cutting process.
Conventional methods for detecting the abrasion degree of the cutting ridge are as follows:
(1) The cutting process is interrupted, and the throw-away tip is removed from the holder to be observed the cutting ridge by means of a tool microscope or the like.
(2) The abrasion degree of the cutting ridge is estimated by detecting a phenomenon incidental to the abrasion of the cutting ridge. For example, a reduction in cutting ability, an increase in vibration, occurrence of a noise, or the like is detected by a sensor disposed adjacent a working portion on a machine tool, and the estimation of the abrasion degree is based on a detection signal from the sensor.
In the method (1), however, the cutting process is interrupted, and the abrasion degree of the cutting ridge cannot quantitatively be determined, so that the abrasion detection cannot accurately be performed.
The method (2) requires a complicated detector, and is less reliable with a poor sensitivity for the detection of the abrasion degree.
One approach to these problems is described in Japanese Unexamined Utility Model Publication No. 3-120323 (1991). This publication discloses a throw-away tip having a sensor line of a conductive film provided along a cutting ridge on a flank thereof. It is also disclosed that the sensor line has a width conforming to an allowable abrasionwidth. In accordance with the throw-away tip disclosed in the publication, the sensor line is worn as the cutting ridge is worn, so that expiration of the life of the cutting ridge can be detected when the sensor line is cut off.
Further, Japanese Unexamined Patent Publication No. 9-38846 (1997) proposes an ordinary cutting tool (not a throw-away tip) which has a thin film circuit on a flank thereof, wherein expiration of the life of the cutting tool is automatically detected by sensing a change in electrical resistance which occurs due to abrasion of the thin film circuit as the flank is worn.
The provision of the sensor line of the conductive film along the cutting ridge on the flank for the detection of the change in the line resistance is preferred for the detection of the abrasion of the cutting ridge.
Where this approach is applied to the throw-away tip, however, it is difficult in practice to connect the sensor line provided along the cutting ridge to an external detection circuit and the like.
More specifically, the throw-away tip is a disposable tip as described above, and is very small with a size of less than 1 cm3. During the cutting process, the tip in operation is exposed to a cutting fluid (water or oil) and shavings. However, no technique has been established for connecting the sensor line formed on the small throw-away tip to the external detection circuit and the like without any trouble in such a machining environment.
The present invention is to provide a throw-away tip having an abrasion sensor which serves for practical implementation to solve the aforesaid problems.
It is a principal object of the present invention to provide a throw-away tip having an abrasion sensor which, when attached to a holder or the like, ensures electrical connection between a sensor line provided thereon and an external circuit without any trouble in a cutting process.
It is another object of the invention to provide a throw-away tip which features protection of a connection portion between a sensor line provided thereon and an external circuit.
In accordance with a first inventive aspect, there is provided a throw-away tip with an abrasion sensor, which comprises: a generally planar base having a rake face defined by one surface thereof, a flank and a restricted face respectively defined by side faces thereof intersecting the rake face, the restricted face being adapted to be fixed in abutment against a restriction face of a holder when the throw-away tip is mounted in the holder; a cutting ridge defined by an intersection between the rake face and the flank; a sensor line of a conductive film provided along the cutting ridge on the flank in an electrically insulative relation with respect to the base; a contact region provided on the restricted face in an electrically insulative relation with respect to the base, the contact region being electrically connectable to an external circuit; and a connection portion provided on the base in an electrically insulative relation with respect to the base and connecting the contact region to an end of the sensor line.
In accordance with a second inventive aspect, the throw-away tip according to the first inventive aspect is characterized in that a cutting nose portion is defined by an intersection between the rake face and two adjacent flanks, wherein the sensor line extends along the cutting ridge as surrounding the nose portion, wherein the contact region includes a pair of contact regions, wherein the connection portion comprises a connection line provided on the flank to connect one of the contact regions on the restricted face to one of opposite ends of the sensor line, and a connection region provided on the rake face to connect the other contact region on the restricted surface to the other end of the sensor line.
In accordance with a third inventive aspect, the throw-away tip according to the second inventive aspect is characterized in that the base has a generally square plan shape and the restricted face includes two restricted faces defined by two side faces opposite from the respective flanks, wherein the one contact region is provided on one of the restricted faces and the other contact region is provided on the other restricted face.
In accordance with a fourth inventive aspect, the throw-away tip according to the second inventive aspect is characterized in that the base has a generally square plan shape and the restricted face includes two restricted faces defined by two side faces opposite from the respective flanks, wherein the pair of contact regions are provided in juxtaposition on one of the restricted faces.
In accordance with a fifth inventive aspect, the throw-away tip according to any of the second to fourth inventive aspects is characterized in that the nose portion includes a plurality of nose portions, wherein a plurality of sensor lines are provided for the respective nose portions, wherein a plurality of connection portions and plural pairs of contact regions connected to the respective sensor lines are provided for the respective nose portions, wherein conduction paths including the sensor lines, the connection portions and the contact regions are arranged in the same pattern.
In the first inventive aspect, the contact regions necessary for connection of the sensor line to a detection circuit and the like are provided on the restricted face which is protected by the restriction face of the holder when the tip is attached to the holder, in the light of the nature of the restricted face.
The throw-away tip generally has a restricted face which is restricted by the restriction face of the holder for prevention of wobble and displacement of the throw-away tip when the throw-away tip is attached to the holder. The restricted face is brought into abutment or intimate contact with the restriction face of the holder.
Therefore, the restricted face is not exposed to the outside but protected by the restriction face with the tip being attached to the holder.
The contact region is provided on the restricted face which, as described above, is not exposed to the outside but protected with the throw-away tip being attached to the holder. If a probe which is electrically connectable to the contact region is provided on the restriction face of the holder, the contact region and the probe are properly connected to each other in an unexposed state.
Therefore, the connection between the contact region and the probe is properly maintained during a cutting process with theuse of the throw-away tip, whereby a change in the resistance of the sensor line can constantly and accurately be detected.
In the second inventive aspect, one of the connection portions is provided on the rake face, so that the electrical conduction path can properly be provided.
In the fifth inventive aspect, the throw-away tip includes the plurality of cutting nose portions, and the plurality of sensor lines are provided for the respective nose portions, whereby the connection portions connected to the sensor lines can be arranged in a smaller space.
Where the base has a generally square plan shape, the flanks are generally defined by two adjacent side faces, and the restricted faces are located opposite from the adjacent side faces. In the third inventive aspect, the one contact region is provided on the one restricted face, while the other contact region is provided on the other restricted face.
In the fourth inventive aspect, the pair of contact regions are provided in juxtaposition on one of the two restricted faces. With this arrangement, a pair of probes are provided on one of the restriction faces of the holder, so that electrical connection between the contact regions and the probes can be established with a simplified construction.
In the fifth inventive aspect, the conductive paths including the sensor lines, the connection portions and the contact regions are arranged in the same pattern. This is advantageous for facilitation of a patterning process and reduction of production costs.
Thus, the present invention provides a throw-away tip with an abrasion sensor, which serves for practical implementation.
With reference to the attached drawings, an explanation will hereinafter be given to specific embodiments of the present invention.